Our long-term goal is to investigate the mechanisms by which insulin signaling effects changes in cellular responses of vascular tissue to other more potent mitogens. We have recently shown that insulin augments the actions of PDGF and VEGF in vascular smooth muscle cells (VSMC) and endothelial cells (EC). Thus, we would like to determine these mechanisms of cross-talk within these cells, determine molecular targets for therapeutic drugs and contribute to the understanding of the pathophysiology of vascular disease in diabetes. We hypothesize that hyperinsulinemia in the state of metabolic insulin resistance, augments the effects of more potent mitogens on the vasculature via increases in prenyltransferase activity, thereby increasing the amounts of prenylated Ras and Rho proteins that are available for mitogen-stimulated GTPloading, resulting in exaggerated cellular responses that lead to the development and progression of atherosclerosis. We will test this hypothesis using two important tools: (1) a dominant-negative mutant of the alpha-subunit (DNFTa) of farnesyltransferase (FTase) and geranylgeranyltransferase I (GGTase I) to help determine the mechanisms that link the insuring signaling pathway to other growth factor pathways, and (2) a tetracyline-inducible system to determine what effects does the expression of DNFTa in stably transfected vascular smooth muscle cells have upon insulin-stimulation of the Erk5 pathway. To determine these mechanisms we have defined three major Specific Aims: (1) Does DNFTa inhibit hyperinsulinemia's ability to potentiate the mitogenic effects of other growth factors in rat aorta vascular smooth muscle cells RASMC in the presence of insulin resistance; (2) Does DNFTa inhibit hyperinsulinemia's ability to potentiate the mitogenic effects of other growth factors in rat pulmonary aortic vascular endothelial cells PAVEC in the presence of insulin resistance; and (3) Does DNFTa inhibit insulin-stimulated phosphorylation, activation and translocation of Erk5 in RASMC in the presence of insulin resistance.